The Program Project "Pulmonary Epithelial in Health and Disease" continues to focus on how airway epithelia function in airways defense. The unifying hypothesis for the Program Project is that endogenous release of nucleotides in response to local str5essres is a major regulator of the fundamental airways defense mechanism, mucus clearance (MC) Four Projects investigate this hypothesis. Dr. Boucher's project tests, in animal models and in man, the hypothesis that (1) airway epithelia release 5' triphosphate nucleotides under basal conditions and in response to physiologic stresses; (2) autocrine regulation of ion transport is effected by nucleotide release, selectively via interaction of lumenal nucleotides with lumenal purinoceptors (P2Y-Rs); nucleotid4e release regulates MC's Dr. Stutts's project tests the hypothesis that: (1) the breakdown of nucleotides by extracellular nucleotidases forms adenosine (ADO) on airway epithelial surfaces that contributes to domain-specific, apical membrane regulation of CFTR C1- channels; (2) the adenosine A2b receptor mediates those responses and is linked to an apical membrane adenylate cyclase that forms cAMP locally in the vicinity of CFTR; (2) the concentration of cAMP in the vicinity of CFTR is regulated by membrane-specific phosphodiesterases; and (4) the reactivity of CFTR to cAMP/protein kinase A-mediated regulation is set by a membrane- specific protein kinase C. Dr. Davis's project will study the relationship between nucleotide release and the regulation of another element of mucus clearance lung defense, ciliary beat frequency (CBF), including: L (1) nucleotide and ADO regulation of CBF; (2) the topography of the membrane-specific nucleotide/ADO effector elements in CBF regulation; and (3) stress-induced nucleotide release and CBF regulation. Dr. Harden's project will study at the molecular level the major apical membrane between P2YY2-Rs and the G proteins that regulate the second messenger activities in airway epithelial cells, including the function of RGS proteins; and (2) the mechanisms of receptor desensitization/sequestration. The PPG is supported by four Cores: An Administrative Core (Core A); a Molecular and Protein Core; a Cell Culture Core and a Nucleotide and Nucleoside Measurement Core. In summary, the PPG will continue to investigate novel hypotheses about the contribution of airway epithelial to lung defense and how to improve the clearance of retained secretions in disease.